Evaluating the potential of Azadirachta indica –assisted zinc oxide particles as efficacious nanofluids by convective experiments with twisted tape annexed circular tube

To cater to the needs of energy sustainability and conservation, reuse of decomposed leaves from trees could reap benefits to biosynthesize nanoparticles that might play a very significant role in the convective performance of nanofluids. Azadirachta indica (neem) possesses capping and reducing agents can assist in fluid stability besides providing good thermal transport behavior in nanofluids. Hence, the synthesis of neem-assisted zinc oxide (ZnOneem) nanoparticles aids in evaluating the role of neem in the thermo-hydraulic behavior as nanofluids. The synthesized particles were 36 nm in size as per the Debye Scherrer relation. Nanofluid samples under particle volume concentrations, ϕ (%) of 0.05, 0.2, and 0.6 with ethylene glycol:water (50:50) as base fluid, were prepared. The optimized stability without surfactants was retrieved by stirring and sonicating at different periods. Convective experiments were done by pumping the fluid turbulently (Re=5000 to 10000) through a circular tube with twisted tape inserts (twist ratio, Y=6, 8, and 10) annexed within it. It was evident that the highest performance evaluation factor (PEF) for ZnOneem was 1.385 while the ZnOpure was 1.289. Though the trade-off existed between the convective performance and frictional drag with ϕ =0.05% ZnOpure nanofluid, it did not exist in the case of ZnOneem nanofluid.